As the production method of (2R,3S)-1-chloro-3-tert-butoxycarbonylamino-4-phenyl-2-butanol, a method comprising chemically reducing amino-protected (3S)-1-halo-3-amino-4-phenyl-2-butanone derivative with a reducing agent such as sodium borohydride and the like is known (patent reference 1, non-patent reference 1). However, this method requires a comparatively expensive reducing agent, and the stereoselectivity thereof is not practically sufficient.
As a method using a microorganism, moreover, a method comprising allowing a microorganism belonging to the genus Candida and the like to act on a (3S)-1-halo-3-amino-4-phenyl-2-butanone derivative to produce a (2R,3S)-1-halo-3-amino-4-phenyl-2-butanol derivative (patent reference 2), and a method comprising bringing a microorganism belonging to the genus Rhodococcus and the like in contact with (3S)-1-halo-2-oxo-3-protected amino-4-substituted butane to produce (2R,3S)-1-halo-2-hydroxy-3-protected amino-4-substituted butane (patent reference 3, non-patent reference 2) are known. By these methods, however, the concentration of the product that can be accumulated in the reaction mixture cannot be practically sufficient.                patent reference 1: JP-A-2-42048        patent reference 2: JP-A-9-285        patent reference 3: WO2002/014528        non-patent reference 1: Tetrahedron, 50, 6333 (1994)        non-patent reference 2: Tetrahedron:Asymmetry, 14, 3105 (2003)        